The present invention relates to level meters, and more particularly to a user selection of meter ballistics that separates a display device from its control circuitry so that different circuitry may be coupled to the display device for different applications.
Many audio devices, such as mixers, tape recorders and amplifiers have level meters to help an operator monitor a signal being passed. Several types of meters have been implemented to cover different applications, operator preferences, etc. Audio consoles designed for radio application typically come equipped with VU meters that indicate average signal levels, but that also have an attack overshoot to help emphasize peak content. Consoles designed for live audio reinforcement may have PPM type meters that give a much more accurate indication of peak material. In both cases, however, there may be a need to have both types of responses available.
Traditionally meters have been implemented as electro-mechanical devices with fixed ballistics, such as attack, decay, overshoot, etc., and frequency response, although electrical networks in the meter drive circuitry may be able alter to some degree these parameters. The general goal of altering the natural response of an electro-mechanical meter is to obtain a more accurate indication of the peak content of the signal. Since the overall meter response is highly dependent on the mechanical characteristics of the meter, ballistics are relatively difficult to control over a wide range.
Recently level meters have been implemented with display devices like LEDs or fluorescent tubes. Examples of these types of devices are disclosed in U.S. Pat. No. 4,528,501 issued July 9, 1985 to Michael L. Dorrough and Kenneth S. Gold entitled "Dual Loudness Meter and Method" and in U.S. Pat. No. 4,679,042 issued July 7, 1987 to Paul M. Trethewey entitled "Bar/Dot Level Meter". Since these devices have no mechanical inertia, all ballistics are generated by the meter drive circuitry. The drive circuitry may be a simple linear amplifier, or it may implement a ballistics standard such as VU or PPM or both. There is generally no choice of ballistics, so in situations where operator preferences or the type of work being done varies a compromise must be made.
What is desired is a level meter that provides an operator with a choice of meter ballistics so that the operator can select for display an appropriate ballistics standard for the work being done.